linux-kernel - Re: [PATCH 3/3] perf annotate: Try chroot filename for objdump

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Date:   Tue, 1 Feb 2022 11:54:14 -0800
From:   Namhyung Kim <namhyung@...nel.org>
To:     Jiri Olsa <jolsa@...hat.com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>
Subject: Re: [PATCH 3/3] perf annotate: Try chroot filename for objdump

Hi Jiri,

On Mon, Jan 31, 2022 at 11:23 AM Jiri Olsa <jolsa@...hat.com> wrote:
>
> On Fri, Jan 28, 2022 at 12:39:50PM -0800, Namhyung Kim wrote:
> > Likewise, it should use a proper name in case the task runs under
> > chroot.  The child_process.err was needed to set to -1 to show error
> > messages properly in TUI.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> > ---
> >  tools/perf/util/annotate.c | 11 +++++++++++
> >  1 file changed, 11 insertions(+)
> >
> > diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
> > index 01900689dc00..e4c641b240df 100644
> > --- a/tools/perf/util/annotate.c
> > +++ b/tools/perf/util/annotate.c
> > @@ -33,6 +33,7 @@
> >  #include "string2.h"
> >  #include "util/event.h"
> >  #include "arch/common.h"
> > +#include "namespaces.h"
> >  #include <regex.h>
> >  #include <pthread.h>
> >  #include <linux/bitops.h>
> > @@ -1696,6 +1697,15 @@ static int dso__disassemble_filename(struct dso *dso, char *filename, size_t fil
> >                * DSO is the same as when 'perf record' ran.
> >                */
> >               __symbol__join_symfs(filename, filename_size, dso->long_name);
> > +
> > +             if (access(filename, R_OK) && errno == ENOENT && dso->nsinfo) {
> > +                     char *new_name = filename_with_chroot(dso->nsinfo->pid,
> > +                                                           filename);
> > +                     if (new_name) {
> > +                             strlcpy(filename, new_name, filename_size);
> > +                             free(new_name);
> > +                     }
> > +             }
> >       }
> >
> >       free(build_id_path);
> > @@ -2036,6 +2046,7 @@ static int symbol__disassemble(struct symbol *sym, struct annotate_args *args)
> >       memset(&objdump_process, 0, sizeof(objdump_process));
> >       objdump_process.argv = objdump_argv;
> >       objdump_process.out = -1;
> > +     objdump_process.err = -1;
>
> is this unrelated fix?

Right, it's unrelated.  Maybe I can split it if Arnaldo wants.

>
> otherwise the whole patchset looks good to me
>
> I guess we'd need to add something like PERF_RECORD_CHROOT to
> handle and instrument sys_chroot to handle this completely?

Are you talking about an env variable?  Maybe we can track
chroot syscall.  But it needs to be task-specific rather than a
global setup.

As it hasn't been an issue so far, I think it's ok to have it as
a fallback right now.

>
> Acked-by: Jiri Olsa <jolsa@...nel.org>

Thanks for your review!
Namhyung


>
> >       if (start_command(&objdump_process)) {
> >               pr_err("Failure starting to run %s\n", command);
> >               err = -1;
> > --
> > 2.35.0.rc2.247.g8bbb082509-goog
> >
>